Power feeding apparatus, transporter and transport system

ABSTRACT

In a power feeding apparatus having pickup coils L 1  and L 2 , a rectifier circuit  4  and output terminals U and V, the relays R 1  and R 2  are connected between the output side terminals of the rectifier circuit  4  and the output terminals U and V Whereas a protective circuit (switching control circuit)  6 , which is connected to the pickup coils L 1  and L 2  and the relay coils r 1  and r 2  to obtain the electric power from the output side terminals of the rectifier circuit  4  in order to carry out ON/OFF control of the relays R 1  and R 2  corresponding to the voltage at the both ends of the pickup coils L 1  and L 2 , is provide. The power feeding apparatus enables to prevent an overcurrent from flowing through a load, to prevent the circuit elements from being destroyed or burnt out due to an overcurrent generated in the pickup coils or an overvoltage generated in a resonance capacitor, to indicate an occurrence of an abnormality and to control the electric power supply by means of a remote control.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a power feeding apparatus thatprevents circuit elements from being destroyed due to an applied overload, and to a transporter and a transport system equipped with thepower feeding apparatus.

[0003] 2. Description of the Related Art

[0004] Conventionally, many transport systems have been realized inorder to transport goods by means of transporters moving along a guiderail, and the efficiency of the transportation of goods within a plantor a warehouse has been increased. Generally, a motor is used to drivesuch a transporter, and the electric power is supplied to the motor viaa feeder line attached along the guide rail.

[0005] As for the power feeding apparatus, there are two types, i.e., atrolley type and a non-contacting type. Because less dust is generatedand less maintenance service is required, the non-contacting type powerfeeding apparatus system is frequently used. In the non-contacting typepower feeding system, a pickup equipped to the transporter is disposedadjacent to the feeder line, and an induced electromotive force isgenerated on the coil by means of the electromagnetic coupling betweenthe pickup and the feeder line to supply the electric power.

[0006]FIG. 1 is a block diagram showing a conventional non-contactingtype power feeding apparatus. In the figure, reference numeral 1 denotesa pickup, which is comprised of a pickup coil L wound around a pickupcore (not shown). The pickup 1 is equipped on a transporter or the likeand is disposed adjacent to the feeder line 9 connected to an electricpower source 11. The feeder line 9 is laid along a guide rail (notshown) or the like disposed within a plant. The transporter is movablealong the guide rail. Connected in parallel to the pickup coil L are aresonance capacitor C and a rectifier circuit 4. The resonance circuit 2is comprised of the coil L and the resonance capacitor C. The outputterminals of the rectifier circuit 4 are connected to the inputterminals of a constant voltage circuit 40, and the output terminals ofthe constant voltage circuit 40 become the output terminals U and V ofthe non-contacting type power feeding apparatus, and at the outputterminals U and V, the driving unit of the transporter is connectedthereto.

[0007] In the non-contacting type power feeding apparatus structured asdescribed above, when AC electric power is supplied to the feeder line 9connected to the electric power source 11, induced electromotive forceis generated on the pickup coil L. The induced electromotive force isresonated in the resonance circuit 2 to obtain maximum electric power,and further, rectified in the rectifier circuit 4, converted intoelectric power having constant voltage characteristic by the constantvoltage circuit 40 and outputted from the output terminals U and V. Theelectric power outputted from the output terminals U and V is suppliedto the driving unit of a transporter or the like (not shown) and thetransporter is driven thereby.

[0008] In the non-contacting type power feeding apparatus describedabove, when the rectifier circuit 4 or the constant voltage circuit 40is opened, or in case the load 10 has an inverter and when the circuitis short circuited, an overcurrent flows through the pickup coil L andresonates resulting in generation of an overvoltage on the resonancecapacitor C. Accordingly, there is a danger that circuit elements may bedestroyed or burnt out due to overheat. Accordingly, in order that aservice person carries out an inspection and repair service on a pointin which the abnormality has occurred, it is necessary to shut down theelectric power source 11 even when the other non-contacting type powerfeeding apparatuses are normal.

[0009] As described above, in the conventional non-contacting type powerfeeding apparatus, when an overcurrent flows through the pickup coil Land resonates, there is a danger that circuit elements may be destroyedor burnt out due to an overvoltage generated on the resonance capacitorC. In order to solve this problem, a non-contacting type power feedingapparatus is disclosed in Japanese Patent Application Laid-Open No.11-164497 (1999). In the above-mentioned non-contacting type powerfeeding apparatus, a thermo-responsive mechanical latch relay having aheat-sensing device installed adjacent to the pickup coil L and acontact provided between the both ends of the pickup coil L or betweenthe output terminals of the rectifier circuit 4, which maintains thecontacting state even when the electric power supply is discontinued, isprovided. When the temperature of the pickup coil L exceeds apredetermined temperature, the contact of the mechanical latch relay isclosed to establish a short circuit between the both ends of the pickupcoil L or between the output terminals of the rectifier circuit 4 sothat the circuit elements are prevented from being destroyed or burntout.

[0010] According to the non-contacting type power feeding apparatusdisclosed in Japanese Patent Application Laid-Open No. 11-164497 (1999),in case an abnormality has occurred, because the input voltage of theconstant voltage circuit 40 becomes zero and no output electric powerremains in the non-contacting type power feeding apparatus, it isimpossible to establish communication with the non-contacting type powerfeeding apparatus in which abnormality occurs, or it is impossible forthe non-contacting type power feeding apparatus to indicate an alarm ofthe abnormality. Further, in case an instantaneous overcurrent flowsthrough the pickup coil L, although the temperature of the pickup coil Lrises, because it takes a relatively long time to reach thepredetermined temperature, there may be a case that an overvoltage isapplied to the circuit elements and they may be destroyed until themechanical latch relay is activated. Furthermore, because a mechanicallatch relay is used, in order to release the latch, which is stopped dueto the abnormality, it is necessary that a service person carry out alatch-releasing service at the position where the abnormality hasoccurred. Still further, in case the non-contacting type power feedingapparatus is installed near the ceiling of a plant, a troublesomenessand danger reside in the service.

[0011] In order to solve the troublesomeness and danger residing in thelatch-releasing service of the above-mentioned mechanical latch relay, anon-contacting type power feeding apparatus is disclosed in JapanesePatent Application Laid-Open No. 11-164498 (1999). In theabove-mentioned non-contacting type power feeding apparatus, athermostat having a contact between the both ends of the pickup coil Lor between the output terminals of the rectifier circuit 4, and aheat-sensing device adjacent to the pickup coil L is provided. When thetemperature of the pickup coil L exceeds a predetermined value, thecontact is closed to prevent the circuit elements from being destroyed,and when the temperature decreases lower than the predetermined value,the contact opens automatically to restart supplying the electric power.

[0012] According to the non-contacting type power feeding apparatusdisclosed in Japanese Patent Application Laid-Open No. 11-164498 (1999),when am abnormality has occurred, even when a service person has notcompleted the inspection and repair service yet, but when thetemperature of the pickup coil L decreases lower than the predeterminedvalue, since the contact of the thermostat opens automatically to returnto the original position, there is a danger that the service person mayget an electric shock, and also, abnormalities due to the identicalcause may be repeated.

BRIEF SUMMARY OF THE INVENTION

[0013] The present invention has been made to solve the above-describedproblems. Accordingly, it is an object of the invention to provide apower feeding apparatus equipped with a switching element connectedbetween the output side terminals of a rectifier circuit and the outputterminals of the power feeding apparatus, which becomes into adiscontinuous state when an overvoltage exceeding a predetermined valuehas occurred at the both ends of the pickup coils due to a short circuitof a load or the like. Accordingly, the power feeding apparatusaccording to the invention enables to prevent an overcurrent fromflowing through the load, and enables to prevent the circuit elementsfrom being destroyed or burnt out due to an overcurrent generated in thepickup coils or an overvoltage generated in the resonance capacitor.Further, the power feeding apparatus according to the invention enablesto make the switching element to become into a discontinuous statewithout any delay at an occurrence of instantaneous overvoltage.

[0014] Further, since the above-mentioned switching circuit isstructured so that the electric power is fed from the output sideterminals of the rectifier circuit, it is possible to provide a powerfeeding apparatus that enables to receive the electric power even whenthe switching element has become into a discontinuous state at anoccurrence of an abnormality, and enables the non-contacting type powerfeeding apparatus itself to indicate an alarm of the abnormality evenwhen an abnormality has occurred.

[0015] Furthermore, in addition to the above, it is another object ofthe invention to provide a power feeding apparatus in which theabove-mentioned switching control circuit is equipped with acommunication unit enabling the switching element to maintain thediscontinuous state and to be controlled by means of a remote control toavoid a danger accompanying the releasing service of the switchingelement and a danger of a service person due to automatic resetting ofthe switching element.

[0016] Still further, it is another object of the invention to provide apower feeding apparatus in which a temperature sensor connected to theabove-mentioned switching control circuit is provided adjacent to thepickup coils, which enables the switching element to become into adiscontinuous state to prevent the circuit elements from being destroyedor burnt out even when the voltage at the both ends of the pickup coilsis lower than a predetermined value, in case the temperature of thepickup coils exceeds a predetermined value due to a temperature risearound the pickup coils or an increase of the electric power or thelike.

[0017] Still furthermore, it is another object of the invention toprovide a power feeding apparatus in which a fuse is provided at theconnecting point between the pickup coils and the switching controlcircuit so that the fuse is opened to prevent the circuit elements frombeing destroyed due to an applied overcurrent or overvoltage even whenan abnormality has occurred in the switching control circuit, theswitching element has become into uncontrollable and an overcurrent hasflowed through the circuit elements.

[0018] Further again, it is another object of the invention to provide atransporter equipped with the above-mentioned power feeding apparatusthat enables to respond to an abnormality occurred while the power issupplied and to provide a stable drive, and a transport system thatincludes the above-mentioned transporter and a feeder line for supplyingthe electric power to the power feeding apparatus mounted on thetransporter to provide a stable drive.

[0019] A power feeding apparatus according to the first invention is apower feeding apparatus, comprising: pickup coils for generating inducedelectromotive force; a rectifier circuit for rectifying the inducedelectromotive force generated on the pickup coils; output terminals foroutputting the output electric power from the rectifier circuit; aswitching element connected between the output terminals of therectifier circuit and the output terminal; and a switching controlcircuit connected to the pickup coils and the switching element forcarrying out ON/OFF control of the switching element corresponding tothe voltage at the both ends of the pickup coils by obtaining theelectric power from the output side terminals of the rectifier circuit.

[0020] A power feeding apparatus according to the second invention is apower feeding apparatus as described in the first invention, furthercomprising a temperature sensor connected to the switching controlcircuit for outputting signals corresponding to the temperature of thepickup coils, wherein the switching control circuit carries out ON/OFFcontrol of the switching element corresponding to the output signals ofthe temperature sensor.

[0021] A power feeding apparatus according to the third invention is apower feeding apparatus as described in the first invention or thesecond invention, further comprising a fuse at a connecting node betweenthe pickup coils and the switching control circuit.

[0022] A power feeding apparatus according to the fourth invention is apower feeding apparatus as described in the first invention or thesecond invention, wherein said switching control circuit comprises acommunication unit.

[0023] A transporter according to the fifth invention is a transporterequipped with any one of the power feeding apparatuses described in thefirst invention through the fourth invention, and is driven by theelectric power supplied by the power feeding apparatus.

[0024] A transport system according to the sixth invention comprises afeeder line connected to an electric power source for generating theinduced electromotive force on the pickup coils, and a transporterdescribed in the fifth invention.

[0025] In the power feeding apparatus according to the first invention,when an overvoltage exceeding a predetermined value has occurred at theboth ends of the pickup coils due to a short circuit or the like of aload, the switching element is made to become into a discontinuous stateby the switching control circuit, and it is possible to prevent anyovervoltage from flowing through the load without stopping the electricpower source. Further, it is possible to prevent the circuit elementsfrom being destroyed or burnt out due to an overcurrent generated on thepickup coils or an overvoltage generated in the resonance capacitor.Furthermore, it is possible to make the switching element to become intoa discontinuous state without any delay at an occurrence ofinstantaneous overvoltage.

[0026] Still further, even when the switching element has become into adiscontinuous state at an occurrence of an abnormality, it is possiblethat the switching control circuit make the power feeding apparatusitself to maintain the indication of the abnormality and to maintain theswitching element in discontinuous state.

[0027] In the power feeding apparatus according to the second invention,even when the voltage generated in the pickup coils is lower than thepredetermined value, but when the temperature of the pickup coilsexceeds the predetermined value due to a temperature rise around thepickup coils or an increase of current or the like, the switchingelement becomes into a discontinuous state to prevent the circuitelements from being destroyed or burnt out.

[0028] In the power feeding apparatus according to the third invention,even when an abnormality has occurred in the switching control circuit,and the switching element has become into uncontrollable and anovercurrent flows, the fuse is opened to prevent the circuit elementsfrom being destroyed or burnt out due to an applied overcurrent orovervoltage.

[0029] In the power feeding apparatus according to the fourth invention,it is possible to control the switching element by means of a remotecontrol. Accordingly, it is possible to eliminate a danger andtroublesomeness accompanying the releasing service of the switchingelement at a position where the power feeding apparatus in which theabnormality has occurred is installed, and to eliminate a danger or thelike of a service person due to automatic resetting of the switchingelement.

[0030] In the transporter according to the fifth invention, it ispossible to respond to an abnormality occurred while the electric poweris supplied and to provide a stable drive.

[0031] In the transport system according to the sixth invention, it ispossible to provide a stable drive and effective transportation ofgoods.

[0032] The above and further objects and features of the invention willmore fully be apparent from the following detailed description withaccompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0033]FIG. 1 is a block diagram showing a conventional non-contactingtype power feeding apparatus;

[0034]FIG. 2 is a block diagram showing an embodiment of anon-contacting type power feeding apparatus according to the presentinvention;

[0035]FIG. 3 is a schematic side view showing the structure of atransporter equipped with the non-contacting type power feedingapparatus in which the power feeding apparatus according to the presentinvention is used;

[0036]FIG. 4 is a block diagram showing the structure of a protectivecircuit (switching control circuit) provided to the non-contacting typepower feeding apparatus which uses the power feeding apparatus accordingto the present invention; and

[0037]FIG. 5 is a schematic perspective view showing a transport systemequipped with the non-contacting type power feeding apparatus in whichthe power feeding apparatus according to the present invention is used.

DETAILED DESCRIPTION OF THE INVENTION

[0038]FIG. 2 is a block diagram showing an embodiment of anon-contacting type power feeding apparatus according to the presentinvention. FIG. 3 is a schematic side view showing the structure of atransporter equipped with the non-contacting type power feedingapparatus.

[0039] In the figures, reference numeral 23 denotes a transporter. Thetransporter 23 is constructed such that a carrier 25 which detachablyattaches goods to be transported is suspended from the lower portion ofa U-shaped chassis frame 24. At upper portion of the chassis frame 24, apickup 1 and a motor M are mounted. Along a guide rail 20 having aroughly I-shaped sectional configuration and laid within a plant, afeeder line 9 is attached therealong. Alternating electric powersupplied from an electric power source 11 to the feeder line 9 generatesthe induced electromotive force caused by the electromagnetic couplingon the pickup 1, and the motor M is driven by electric power and thetransporter 23 is driven accordingly. A driving wheel 24 a provided onthe transporter 23 rotatably comes in contact with the upper face of anupper plan portion 20 u of the guide rail 20, and the transporter 23travels along the guide rail 20.

[0040] The pickup 1 is comprised of pickup coils L1 and L2 wound arounda pickup core (not shown) respectively. A resonance capacitor C1 isconnected in parallel to the pickup coils L1 and L2. A resonance circuit2 is comprised of the pickup coils L1 and L2 and the resonance capacitorC1. Further, a fuse F is connected in series between the pickup coil L1and the connecting node to which the resonance capacitor C1.

[0041] To the resonance capacitor 1, a capacitor C2 is connected inparallel, and a coil L3 and a capacitor C3 connected in series areconnected in parallel. A η-type (C-L-C type) immittance conversioncircuit 3 is comprised of the capacitors C2, C3 and the coil L3. Thecommon connecting node of the capacitor C3 and the coil L3, and thecommon connecting node of the capacitor C2 and the capacitor C3 are theconnecting nodes, respectively, with the input-side terminals of arectifier circuit 4. A capacitor C4 is connected in parallel to theoutput side terminals of the rectifier circuit 4, and one terminal ofeach relay of R1 and R2, which are the switching elements, is connectedto the output side terminals thereof respectively. The other terminalsof each relay R1 and R2 becomes the output terminals U and V,respectively, of the non-contacting type power feeding apparatus andconnected to the load 10 such as the motor M of the transporter 23.

[0042] A temperature sensor 7 that has contacts positioned at the bothends of the resonance capacitor C1 and adjacent to the pickup coils L1and L2 is connected to a protective circuit (switching control circuit)6. The protective circuit 6 is connected to each relay coil r1 and r2 ofthe relays R1 and R2, and is provided with an antenna W comprising acommunication unit and an alarm 12, and is supplied with the electricpower from the output side terminals of the rectifier circuit 4 via aDC/DC converter 8. The temperature sensor 7 is positioned adjacent tothe pickup coils L1 and L2 and, in order to reduce the influence of themagnetic field, disposed at right angles to the magnetic field generatedon the pickup cores, and a non-metallic temperature sensor such as athermo-sensitive ferrite or a thermistor is used. In the non-contactingtype power feeding apparatus, the circuit portion excluding the pickup 1is contained within a circuit box 30 provided to the upper portion ofthe chassis frame 24 of the transporter 23.

[0043]FIG. 4 is a block diagram showing the structure of the protectivecircuit 6 provided to the non-contacting type power feeding apparatusthat uses the power feeding apparatus according to the invention. Thevoltage generated at the both ends of the resonance capacitor C1 isconverted into DC voltage and smoothed by a rectifying and smoothingcircuit 62 comprising the protective circuit 6, and compared with athreshold voltage by a comparison circuit 63 such as a comparator. Sincea photocoupler 64 is interposed between the comparison circuit 63 and arelay sequence circuit 61, the output signals of the comparison circuit63 are transmitted while being isolated to the relay sequence circuit61, converted into control signals for carrying out ON/OFF control ofthe relays R1 and R2 and inputted to the relay coils r1 and r2.

[0044] The temperature sensor 7 detects the voltage signalscorresponding to the temperature of the pickup coils L1 and L2 and inputthem to the relay sequence circuit 61. Further, the temperature sensor 7is provided with a contact 71, and the contact 71 carries out contactingoperation corresponding to the temperature of the pickup coils L1 andL2. That is to say, when the temperature of the pickup coils L1 and L2is lower than the threshold value, the contact 71 closes the circuit(OFF), and when it is higher than the threshold value, the contact 71opens the circuit (ON). The voltage signals are converted into thecontrol signals for carrying out ON/OFF control of the relays R1 and R2and inputted into the relay coils r1 and r2.

[0045] Hereinafter, a description will be made as to the operation ofthe non-contacting type power feeding apparatus structured as describedabove.

[0046] When the AC electric power having a constant currentcharacteristic is supplied to the feeder line 9 connected to theelectric power source 11, an induced electromotive force having aconstant current characteristic is generated on the pickup coils L1 andL2 of the pickup 1. The induced electromotive force is resonated in theresonance circuit 2 and its voltage is increased, at the same time,reactive power elements are removed, and the constant currentcharacteristic is converted into constant voltage characteristic by theimmittance conversion circuit 3. Further, the electric power isrectified by the rectifier circuit 4 and smoothed by the capacitor C4,and outputted from the output terminals U and V via the relays R1 and R2in the open circuit state. When the electric power is supplied to theload 10 such as the motor M or the like of the transporter 23, thetransporter 23 is driven.

[0047] Whereas, the protective circuit 6 is supplied with electric powerfrom the output side terminal of the rectifier circuit 4 via the DC/DCconverter 8, and receives the signals corresponding to the voltagegenerated at the both ends of the resonance capacitor C1 and the signalscorresponding to the temperature of the pickup coils L1 and L2 detectedby the temperature sensor 7.

[0048] When an abnormality such as a short circuit or the like occurs inan built-in circuit of the load 10, since the state is the identical asa state in which the output terminals U and V of the non-contacting typepower feeding apparatus are short circuited, an overcurrent flowsthrough the pickup coils L1 and L2, and overvoltage is generated in theresonance capacitor C1. When the voltage generated in the resonancecapacitor C1 exceeds the threshold value, the relays R1 and R2 are shutdown (closed circuit)by the protective circuit 6, at the same time thealarm 12 is activated. Also, even when the voltage generated in theresonance capacitor C1 is lower than the threshold value, but when thetemperature around the pickup coils L1 and L2 increases, or thetemperature of the pickup coils L1 and L2 increases due to an increaseof the electric power or the like, and when the temperature detected bythe temperature sensor 7 exceeds the threshold value, the relays R1 andR2 are shut down by the protective circuit 6, and at the same time thealarm 12 is activated.

[0049] In the non-contacting type power feeding apparatus as describedabove, when the relays R1 and R2 are shut down, although the outputelectric power of the non-contacting type power feeding apparatusbecomes zero, because the protective circuit 6 can receive electricpower from the output side terminals of the rectifier circuit 4 via theDC/DC converter 8, it is possible to maintain the state in which therelays R1 and R2 are shut down and the alarm 12 is activated.

[0050] While the state under which the relays R1 and R2 are shut down ismaintained, a necessary measures such as an inspection and repairservice or the like of the abnormality occurred on the load 10 of thetransporter or the like will be taken. And after that, an instructionsignals to make the relays R1 and R2 to open are sent to the protectivecircuit 6 from the outside via the antenna W. The protective circuit 6controls the relays R1 and R2 to open in accordance with the instructionsignals, and the load 10 of the transporter or the like is supplied withelectric power from the non-contacting type power feeding apparatus anddriven again.

[0051] Furthermore, in case an abnormality has occurred on any one ofthe immittance conversion circuit 3, rectifier circuit 4, relays R1 andR2 or protective circuit 6, and the relays R1 and R2 have becomeuncontrollable, and furthermore an overcurrent has flowed through thepickup coils L1 and L2, the fuse F is opened and the electric powersupplied by the non-contacting type power feeding apparatus in which theabnormality has occurred is stopped forcedly.

[0052] As for the immittance conversion circuit 3, in addition to thetype shown in FIG. 2, any type of immittance conversion circuit fromη-type (L-C-L type), T-type (C-L-C type), T-type (L-C-L type), andcross-type may be used. Further, in place of the immittance conversioncircuit, a constant-voltage circuit may be used. In the protectivecircuit 6 according to the embodiment of the invention, in order tocontrol the voltage at both ends of the resonance capacitor C1 and thetemperature of the pickup coils L1 and L2, the relays R1 and R2 arecontrolled. In addition, in order to control each of the current of theresonance capacitor C1, the current of the pickup coils L1 and L2, theoutput current of the immittance conversion circuit 3 and the DC outputcurrent of the rectifier circuit 4, using a value detected by a currenttransformer or a shunt resistance, or a value detected using the voltageat the both ends of the coil L3, or a value of the magnetic flux densitydetected using the search coil, the relays R1 and R2 may be controlled.Still further, as for switching element, in addition to the relays, atransistor or thyrister may be used.

[0053]FIG. 5 is a schematic perspective view showing a transport systemequipped with the non-contacting type power feeding apparatus in whichthe power feeding apparatus according to the invention is used. In thetransport system, the feeder line (refer to FIG. 3) is attached alongthe guide rail 20 laid in a plant and connected to the electric powersource 11. A plurality of the transporters 23 shown in FIG. 5 is hung tothe guide rail 22, and controlled by the system controller 20 and drivento carry the goods to be transported. As described in the non-contactingtype power feeding apparatus shown in FIG. 2, when an abnormality suchas an open circuit of the non-contacting type power feeding apparatus ora short circuit of the transporter 23 or the like has occurred while thetransporter 23 is driven, the electric power supply is stopped by theprotective circuit 6 provided to the non-contacting type power feedingapparatus, and the alarm 12 is activated to alert to the occurrence ofthe abnormality.

[0054] The power feeding apparatus according to the first inventionenables the switching element to become into a discontinuous state toprevent any overvoltage from flowing through the load without stoppingthe electric power source, when an overvoltage exceeding a predeterminedvalue has generated at the both ends of the pickup coils due to a shortcircuit of the load or the like. Further, the power feeding apparatusaccording to the first invention enables to prevent the circuit elementsfrom being destroyed or burnt out due to an overcurrent generated in thepickup coils or an overvoltage generated in the resonance capacitor.Furthermore, the power feeding apparatus according to the firstinvention enables to make the switching element to become into adiscontinuous state without any delay at an occurrence of instantaneousovervoltage. Still further, even when an abnormality has occurred, thepower feeding apparatus according to the first invention enables thepower feeding apparatus itself to indicate an alarm of the abnormality.

[0055] The power feeding apparatus according to the second inventionenables to make the switching element to become into a discontinuousstate to prevent the circuit elements from being destroyed or burnt outeven when the voltage generated at the both ends of the pickup coils islower than the above-mentioned predetermined value, but when thetemperature of the pickup coils exceeds the predetermined value due to atemperature rise around the pickup coils or an increase of current orthe like.

[0056] The power feeding apparatus according to the third inventionenables to make the fuse open to prevent the circuit elements from beingdestroyed or burnt out due to an applied overcurrent or overvoltage,even when an abnormality has occurred in the switching control circuit,the switching element has become into uncontrollable and an overcurrenthas flowed.

[0057] The power feeding apparatus according to the fourth inventionenables to control the switching element by means of a remote controlresulting in elimination of a danger and troublesomeness accompanyingthe releasing service of the switching element carried out at a positionwhere the power feeding apparatus in which the abnormality has occurredis installed, and elimination of danger of a service person due toautomatic resetting of the switching element.

[0058] The transporter according to the fifth invention enables torespond to an abnormality occurred while the electric power is suppliedand to provide a stable drive.

[0059] The transport system according to the sixth invention enables toprovide a stable drive and effective transportation of objects.

[0060] As this invention may be implemented in several forms withoutdeparting from the spirit of essential characteristics thereof, thepresent embodiment is therefore illustrative and not restrictive, sincethe scope of the invention is defined by the appended claims rather thanby the description preceding them, and all changes that fall withinmetes and bounds of the claims, or equivalence of such metes and boundsthereof are therefore intended to be embraced by the claims.

1. A power feeding apparatus, comprising: pickup coils for generatinginduced electromotive force; a rectifier circuit for rectifying theinduced electromotive force generated on said pickup coils; outputterminals for outputting the output electric power from said rectifiercircuit; a switching element connected between said output terminals ofsaid rectifier circuit and said output terminals; and a switchingcontrol circuit connected to said pickup coils and said switchingelement for carrying out ON/OFF control of said switching elementcorresponding to the voltage at the both ends of said pickup coils byobtaining the electric power from the output side terminals of saidrectifier circuit.
 2. The power feeding apparatus as set forth in claim1, further comprising a fuse at a connecting node between said pickupcoils and said switching control circuit.
 3. The power feeding apparatusas set forth in claim 1, wherein said switching control circuitcomprises a communication unit.
 4. The power feeding apparatus as setforth in claim 1, further comprising a temperature sensor connected tosaid switching control circuit for outputting signals corresponding tothe temperature of said pickup coils, wherein said switching controlcircuit carries out ON/OFF control of said switching elementcorresponding to the output signals of said temperature sensor.
 5. Thepower feeding apparatus as set forth in claim 4, further comprising afuse at a connecting node between said pickup coils and said switchingcontrol circuit.
 6. The power feeding apparatus as set forth in claim 4,wherein said switching control circuit comprises a communication unit.7. A transporter, comprising a power feeding apparatus as set forth inclaim 1, and driven by the electric power supplied by said power feedingapparatus.
 8. The transporter as set forth in claim 7, furthercomprising a fuse at a connecting node between said pickup coils andsaid switching control circuit.
 9. The transporter as set forth in claim7, wherein said switching control circuit comprises a communicationunit.
 10. The transporter as set forth in claim 7, further comprising atemperature sensor connected to said switching control circuit foroutputting signals corresponding to the temperature of said pickupcoils, wherein said switching control circuit carries out ON/OFF controlof said switching element corresponding to the output signals of saidtemperature sensor.
 11. The transporter as set forth in claim 10,further comprising a fuse at a connecting node between said pickup coilsand said switching control circuit.
 12. The transporter as set forth inclaim 10, wherein said switching control circuit comprises acommunication unit.
 13. A transport system, comprising: a feeder lineconnected to an electric power source for generating inducedelectromotive force on a pickup; and a transporter as set forth in claim7.
 14. The transport system as set forth in claim 13, further comprisinga fuse at a connecting node between said pickup coils and said switchingcontrol circuit.
 15. The transport system as set forth in claim 13,wherein said switching control circuit comprises a communication unit.16. the transport system as set forth in claim 13, further comprising atemperature sensor connected to said switching control circuit foroutputting signals corresponding to the temperature of said pickupcoils, wherein said switching control circuit carries out ON/OFF controlof said switching element corresponding to the output signals of saidtemperature sensor.
 17. The transport system as set forth in claim 16,further comprising a fuse at a connecting node between said pickup coilsand said switching control circuit.
 18. The transport system as setforth in claim 16, wherein said switching control circuit comprises acommunication unit.